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<title>Struct template callable_eval</title>
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<a name="boost.proto.context.callable_eval"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Struct template callable_eval</span></h2>
<p>boost::proto::context::callable_eval — A BinaryFunction that accepts a Proto expression and a callable context and calls
            the context with the expression tag and children as arguments, effectively fanning the
            expression out. </p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../../proto/reference.html#header.boost.proto.context.callable_hpp" title="Header &lt;boost/proto/context/callable.hpp&gt;">boost/proto/context/callable.hpp</a>&gt;

</span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <a class="link" href="../../../Expr.html" title="Concept Expr">Expr</a><span class="special">,</span> <span class="keyword">typename</span> Context<span class="special">&gt;</span> 
<span class="keyword">struct</span> <a class="link" href="callable_eval.html" title="Struct template callable_eval">callable_eval</a> <span class="special">{</span>
  <span class="comment">// types</span>
  <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">&lt;</span>
    <span class="identifier">Context</span><span class="special">(</span>
      <span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">::</span><span class="identifier">proto_tag</span><span class="special">,</span>
      <span class="keyword">typename</span> <span class="identifier">proto</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">child_c</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span><span class="special">,</span>
      <span class="special">...</span>
      <span class="keyword">typename</span> <span class="identifier">proto</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">child_c</span><span class="special">&lt;</span><span class="identifier">N</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span><span class="special">,</span>
    <span class="special">)</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span>
   <a name="boost.proto.context.callable_eval.result_type"></a><span class="identifier">result_type</span><span class="special">;</span>

  <span class="comment">// <a class="link" href="callable_eval.html#id-1_3_34_5_54_2_1_1_1_5-bb">public member functions</a></span>
  <span class="identifier">result_type</span> <a class="link" href="callable_eval.html#id-1_3_34_5_54_2_1_1_1_5_1-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">Expr</span> <span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Context</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="id-1.3.34.5.56.4.4"></a><h2>Description</h2>
<p>
              <code class="computeroutput">proto::context::callable_eval&lt;&gt;</code> requires that
              <code class="computeroutput">Context</code> is a <a class="link" href="../../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a>
              that can be invoked with <code class="computeroutput">Expr</code>'s tag and children as
              expressions, as follows:
              </p>
<pre class="programlisting"><span class="identifier">context</span><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">::</span><span class="identifier">proto_tag</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> <a class="link" href="../child_c.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span><span class="special">,</span> <span class="special">...</span> <a class="link" href="../child_c.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="identifier">N</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span><span class="special">)</span></pre>
<p>
            </p>
<div class="refsect2">
<a name="id-1.3.34.5.56.4.4.3"></a><h3>
<a name="id-1_3_34_5_54_2_1_1_1_5-bb"></a><code class="computeroutput">callable_eval</code> public member functions</h3>
<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
<pre class="literallayout"><span class="identifier">result_type</span> <a name="id-1_3_34_5_54_2_1_1_1_5_1-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">Expr</span> <span class="special">&amp;</span> expr<span class="special">,</span> <span class="identifier">Context</span> <span class="special">&amp;</span> context<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
<div class="variablelist"><table border="0" class="variablelist compact">
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<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
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<td><p><span class="term"><code class="computeroutput">context</code></span></p></td>
<td><p>The callable evaluation context </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">expr</code></span></p></td>
<td><p>The current expression </p></td>
</tr>
</tbody>
</table></div></td>
</tr>
<tr>
<td><p><span class="term">Returns:</span></p></td>
<td><p>
                  <code class="computeroutput">
                    context(typename Expr::proto_tag(),
                    <a class="link" href="../child_c.html" title="Function child_c">proto::child_c</a>&lt;0&gt;(expr),...
                    <a class="link" href="../child_c.html" title="Function child_c">proto::child_c</a>&lt;N&gt;(expr))
                  </code>
                </p></td>
</tr>
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<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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